STK984-091A-E

Summary description
The STHS4257 is an IEEE802.3af-compliant family of interface controllers for Power over Ethernet (PoE) Powered Device (PD) applications.
The devices consist of two main sections:●
The IEEE802.3af interface to the PoE powered RJ-45 wall socket, and● the Hot Swap Controller (HSC) functions required to protect the PD during insertion, operation, and withdrawal from the RJ-45 socket.
These devices have an integrated high voltage power MOSFET (low-side switch) with low RON and the capability to accept transients as high as 100V. Since the pins (such as GND and VIN) which interface to the RJ-45 socket can routinely see high peak voltages in excess of 100V, it is strongly recommended that board designers protect the PD device with a transient voltage suppressor, such as the SMAJ58A (available from STMicroelectronics), connected between the GND and VIN pins (see Figure 4 on page 8).
Features
• IEEE 802.3af-compliant interface for Powered Devices (PDs)
• Integrated 100V, 450mA power MOSFET low side switch
• Inrush current limit
• Normal operation current limit
• Integrated 25kΩ signature resistor
• Signature disable (STHS4257A1/L1)
• Resistor-programmable classification current (Class 0-4)
• Power Good output, open drain
• Undervoltage Lockout (UVLO)
•
Thermal overload protection (two-step for the STHS4257A/L)
• Latch (L) or auto-retry (A) after repetitive thermal overload
• Industrial temperature range: –40 to +85°C
• SO8 and DFN8 (3mm x 3mm) packages
• RoHS compliantApplications
• Voice over IP (VoIP) phones
• Web cameras
• WLAN access points
• Internet appliances
• POS terminals
• RFID readers